Here is a picture of Frisco rebuilt single sheathed boxcar with dark chalk marks high enough up that likely written at the loading platform:

https://donstrack.smugmug.com/UtahRails/Emil-Albrecht-Photos/1947-Sep-Salt-Lake-City/i-jV3JmGN/A 

Gary Laakso

south of Mike Brock

In the next picture, are those military vehicles on the flat cars in front of the UP caboose?